The reaction of p-nitrocumyl bromide (RBr) with sodium nitrite in [2H6]dimethyl sulfoxide gives none of the conventional evidence for an SRN1 chain reaction but the initial values of the [RNO2]/[RONO] ratio (2.5–5) are far higher than would be expected for the attack of a nitrite ion on the carbocation R+ and increase with the concentration of nitrite ions. The high values of [RNO2]/[RONO] are considered to derive from a mechanism in which a nitrite ion attacks a π-complex derived from the carbocation R+ and a second nitrite ion. This interpretation is supported by a kinetic term that is second order with respect to nitrite ions. An attempt to provide evidence for alternative radical pair intermediates from 15N CIDNP effects was unsuccessful.
对硝基二茂
溴(RBr)与
亚硝酸钠在[2H6]
二甲基亚砜中的反应没有给出 SRN1 链式反应的常规证据,但[RNO2]/[RONO]比值(2.5-5)的初始值远高于
亚硝酸根离子攻击碳化合物 R+ 的预期值,并且随着
亚硝酸根离子浓度的增加而增加。据认为,[RNO2]/[RONO]的高值源于
亚硝酸根离子攻击由碳位 R+ 和第二个
亚硝酸根离子生成的 π-复合物的机制。这一解释得到了与
亚硝酸根离子有关的二阶动力学项的支持。试图从 15N CIDNP 效应中提供替代自由基对中间体的证据,但没有成功。